1. Field of the Invention
This invention relates generally to a method and apparatus for editing magnetic recording media and, more particularly, to an editing method and edit-mode controller intended for use with at least two video tape recorders.
2. Description of the Background
During an editing operation on a long-playing video tape using conventional video tape recorders (VTRs), it is frequently necessary to place one or both of the VTRs into a so-called still mode, wherein the rotary head repeatedly scans the same location on the tape. For example, when dubbing is performed using two VTRs, in which one reproduces the video signal of a desired program recorded on a respective tape while the other VTR records that reproduced video signal at a designated portion on another video tape, it is necessary to search for a reproducing start point and a recording start point on the respective video tapes. Such searching cannot typically be performed simultaneously so that if the recording start point is being searched for in the recording VTR after the reproducing start point has already been determined in the playback VTR, the latter VTR must be placed in the still mode until the recording start point is determined. One video tape editor known heretofore is described in U.S. Pat. No. 4,463,391 and operates to place the video tape recorder in a pause mode, corresponding to the above-described still mode, and the tape is returned mechanically for a short distance in order to place it in a proper position so that when the video tape recorder commences recording, the track pitch of the previously recorded portion and the newly recorded portion will be substantially identical.
Video tape recorders are typically constructed so that the heads are mounted on a rotary drum to be in contact with the magnetic tape and scan at a relatively high rotational rate. Therefore, if the video tape recorder remains for a relatively long period of time in the still or pause mode, in which the magnetic tape is stopped yet the rotary heads continue to rotate, a portion of magnetic tape at that location is subject to repeated contact by the heads, and the tape is likely to have its magnetic layer damaged. Not only does such tape damage occur but frequently a transfer of the magnetic particles from the tape to the head will also take place. In any event, both of these possible conditions will result in a signal dropout upon reproduction in the normal mode of signals recorded at that location on the tape.
One approach that has been proposed to overcome this problem when the still mode continues for a lengthy period of time is to automatically release the VTR from the still mode after a predetermined period of time has elapsed. This, of course, will protect the tape from degradation caused by the repeated scanning of the VTR heads at the same location. For example, after six minutes have elapsed in the still mode, the VTR used for recording is released from the still mode during the time that the desired portion on the tape to be reproduced is being searched for by the playback VTR. The problem then is once the desired portion to be reproduced is found by the reproducing VTR, the recording VTR has already run its tape at a normal speed so that it is necessary to once again search for the recording starting point on the tape by the recording VTR. It has been found that if a VTR is released from the still mode during such editing procedures described above, it takes a relatively long period of time to complete the overall editing operation.